[ViewVC] Diff of: cvs/BDB/BDB.pm

Comparing BDB/BDB.pm (file contents):
Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs.
Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use BDB;	7	use BDB;
8		8
		9	my $env = db_env_create;
		10
		11	mkdir "bdtest", 0700;
		12	db_env_open
		13	$env,
		14	"bdtest",
		15	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL
		16	\| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		17	0600;
		18
		19	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		20
		21	my $db = db_create $env;
		22	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE
		23	\| BDB::READ_UNCOMMITTED, 0600;
		24	db_put $db, undef, "key", "data", 0, sub {
		25	db_del $db, undef, "key";
		26	};
		27	db_sync $db;
		28
		29	# when you also use Coro, management is easy:
		30	use Coro::BDB;
		31
		32	# automatic event loop intergration with AnyEvent:
		33	use AnyEvent::BDB;
		34
		35	# automatic result processing with EV:
		36	my $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
		37
		38	# with Glib:
		39	add_watch Glib::IO BDB::poll_fileno,
		40	in => sub { BDB::poll_cb; 1 };
		41
		42	# or simply flush manually
		43	BDB::flush;
		44
		45
9	=head1 DESCRIPTION	46	=head1 DESCRIPTION
10		47
11	See the eg/ directory in the distribution and the berkeleydb C	48	See the BerkeleyDB documentation (L<http://www.oracle.com/technology/documentation/berkeley-db/db/index.html>).
12	documentation. This is inadequate, but the only sources of documentation	49	The BDB API is very similar to the C API (the translation has been very faithful).
13	known for this module so far.
14		50
15	=head2 EXAMPLE	51	See also the example sections in the document below and possibly the eg/
		52	subdirectory of the BDB distribution. Last not least see the IO::AIO
		53	documentation, as that module uses almost the same asynchronous request
		54	model as this module.
		55
		56	I know this is woefully inadequate documentation. Send a patch!
		57
16		58
17	=head1 REQUEST ANATOMY AND LIFETIME	59	=head1 REQUEST ANATOMY AND LIFETIME
18		60
19	Every request method creates a request. which is a C data structure not	61	Every request method creates a request. which is a C data structure not
20	directly visible to Perl.	62	directly visible to Perl.
…		…
66	no warnings;	108	no warnings;
67	use strict 'vars';	109	use strict 'vars';
68		110
69	use base 'Exporter';	111	use base 'Exporter';
70		112
		113	our $VERSION;
		114
71	BEGIN {	115	BEGIN {
72	our $VERSION = '0.1';	116	$VERSION = '1.81';
73		117
74	our @BDB_REQ = qw(	118	our @BDB_REQ = qw(
75	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect	119	db_env_open db_env_close db_env_txn_checkpoint db_env_lock_detect
76	db_env_memp_sync db_env_memp_trickle	120	db_env_memp_sync db_env_memp_trickle db_env_dbrename db_env_dbremove
77	db_open db_close db_compact db_sync db_put db_get db_pget db_del db_key_range	121	db_env_log_archive
		122	db_open db_close db_compact db_sync db_upgrade
		123	db_put db_exists db_get db_pget db_del db_key_range
78	db_txn_commit db_txn_abort	124	db_txn_commit db_txn_abort db_txn_finish
79	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del	125	db_c_close db_c_count db_c_put db_c_get db_c_pget db_c_del
80	db_sequence_open db_sequence_close	126	db_sequence_open db_sequence_close
81	db_sequence_get db_sequence_remove	127	db_sequence_get db_sequence_remove
82	);	128	);
83	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));	129	our @EXPORT = (@BDB_REQ, qw(dbreq_pri dbreq_nice db_env_create db_create));
…		…
90		136
91	require XSLoader;	137	require XSLoader;
92	XSLoader::load ("BDB", $VERSION);	138	XSLoader::load ("BDB", $VERSION);
93	}	139	}
94		140
		141	=head1 BERKELEYDB FUNCTIONS
		142
		143	All of these are functions. The create functions simply return a new
		144	object and never block. All the remaining functions take an optional
		145	callback as last argument. If it is missing, then the function will be
		146	executed synchronously. In both cases, C<$!> will reflect the return value
		147	of the function.
		148
		149	BDB functions that cannot block (mostly functions that manipulate
		150	settings) are method calls on the relevant objects, so the rule of thumb
		151	is: if it's a method, it's not blocking, if it's a function, it takes a
		152	callback as last argument.
		153
		154	In the following, C<$int> signifies an integer return value,
		155	C<bdb_filename> is a "filename" (octets on unix, madness on windows),
		156	C<U32> is an unsigned 32 bit integer, C<int> is some integer, C<NV> is a
		157	floating point value.
		158
		159	Most C<SV *> types are generic perl scalars (for input and output of data
		160	values).
		161
		162	The various C<DB_ENV> etc. arguments are handles return by
		163	C<db_env_create>, C<db_create>, C<txn_begin> and so on. If they have an
		164	appended C<_ornull> this means they are optional and you can pass C<undef>
		165	for them, resulting a NULL pointer on the C level.
		166
		167	The C<SV *callback> is the optional callback function to call when the
		168	request is completed. This last callback argument is special: the callback
		169	is simply the last argument passed. If there are "optional" arguments
		170	before the callback they can be left out. The callback itself can be left
		171	out or specified as C<undef>, in which case the function will be executed
		172	synchronously.
		173
		174	For example, C<db_env_txn_checkpoint> usually is called with all integer
		175	arguments zero. These can be left out, so all of these specify a call
		176	to C<< DB_ENV->txn_checkpoint >>, to be executed asynchronously with a
		177	callback to be called:
		178
		179	db_env_txn_checkpoint $db_env, 0, 0, 0, sub { };
		180	db_env_txn_checkpoint $db_env, 0, 0, sub { };
		181	db_env_txn_checkpoint $db_env, sub { };
		182
		183	While these all specify a call to C<< DB_ENV->txn_checkpoint >> to be
		184	executed synchronously:
		185
		186	db_env_txn_checkpoint $db_env, 0, 0, 0, undef;
		187	db_env_txn_checkpoint $db_env, 0, 0, 0;
		188	db_env_txn_checkpoint $db_env, 0;
		189
		190	=head2 BDB functions
		191
		192	Functions in the BDB namespace, exported by default:
		193
		194	$env = db_env_create (U32 env_flags = 0)
		195	flags: RPCCLIENT
		196
		197	db_env_open (DB_ENV env, bdb_filename db_home, U32 open_flags, int mode, SV callback = &PL_sv_undef)
		198	open_flags: INIT_CDB INIT_LOCK INIT_LOG INIT_MPOOL INIT_REP INIT_TXN RECOVER RECOVER_FATAL USE_ENVIRON USE_ENVIRON_ROOT CREATE LOCKDOWN PRIVATE REGISTER SYSTEM_MEM
		199	db_env_close (DB_ENV env, U32 flags = 0, SV callback = &PL_sv_undef)
		200	db_env_txn_checkpoint (DB_ENV env, U32 kbyte = 0, U32 min = 0, U32 flags = 0, SV callback = &PL_sv_undef)
		201	flags: FORCE
		202	db_env_lock_detect (DB_ENV env, U32 flags = 0, U32 atype = DB_LOCK_DEFAULT, SV dummy = 0, SV *callback = &PL_sv_undef)
		203	atype: LOCK_DEFAULT LOCK_EXPIRE LOCK_MAXLOCKS LOCK_MAXWRITE LOCK_MINLOCKS LOCK_MINWRITE LOCK_OLDEST LOCK_RANDOM LOCK_YOUNGEST
		204	db_env_memp_sync (DB_ENV env, SV dummy = 0, SV *callback = &PL_sv_undef)
		205	db_env_memp_trickle (DB_ENV env, int percent, SV dummy = 0, SV *callback = &PL_sv_undef)
		206	db_env_dbremove (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, U32 flags = 0, SV *callback = &PL_sv_undef)
		207	db_env_dbrename (DB_ENV env, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, bdb_filename newname, U32 flags = 0, SV *callback = &PL_sv_undef)
		208	db_env_log_archive (DB_ENV env, SV listp, U32 flags = 0, SV *callback = &PL_sv_undef)
		209
		210	$db = db_create (DB_ENV *env = 0, U32 flags = 0)
		211	flags: XA_CREATE
		212
		213	db_open (DB db, DB_TXN_ornull txnid, bdb_filename file, bdb_filename database, int type, U32 flags, int mode, SV *callback = &PL_sv_undef)
		214	flags: AUTO_COMMIT CREATE EXCL MULTIVERSION NOMMAP RDONLY READ_UNCOMMITTED THREAD TRUNCATE
		215	db_close (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		216	flags: DB_NOSYNC
		217	db_upgrade (DB db, bdb_filename file, U32 flags = 0, SV callback = &PL_sv_undef)
		218	db_compact (DB db, DB_TXN_ornull txn = 0, SV start = 0, SV stop = 0, SV unused1 = 0, U32 flags = DB_FREE_SPACE, SV unused2 = 0, SV *callback = &PL_sv_undef)
		219	flags: FREELIST_ONLY FREE_SPACE
		220	db_sync (DB db, U32 flags = 0, SV callback = &PL_sv_undef)
		221	db_key_range (DB db, DB_TXN_ornull txn, SV key, SV key_range, U32 flags = 0, SV *callback = &PL_sv_undef)
		222	db_put (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		223	flags: APPEND NODUPDATA NOOVERWRITE
		224	db_exists (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = 0) (v4.6)
		225	db_get (DB db, DB_TXN_ornull txn, SV key, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		226	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		227	db_pget (DB db, DB_TXN_ornull txn, SV key, SV pkey, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		228	flags: CONSUME CONSUME_WAIT GET_BOTH SET_RECNO MULTIPLE READ_COMMITTED READ_UNCOMMITTED RMW
		229	db_del (DB db, DB_TXN_ornull txn, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		230	db_txn_commit (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		231	flags: TXN_NOSYNC TXN_SYNC
		232	db_txn_abort (DB_TXN txn, SV callback = &PL_sv_undef)
		233
		234	db_c_close (DBC dbc, SV callback = &PL_sv_undef)
		235	db_c_count (DBC dbc, SV count, U32 flags = 0, SV *callback = &PL_sv_undef)
		236	db_c_put (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		237	flags: AFTER BEFORE CURRENT KEYFIRST KEYLAST NODUPDATA
		238	db_c_get (DBC dbc, SV key, SV data, U32 flags = 0, SV callback = &PL_sv_undef)
		239	flags: CURRENT FIRST GET_BOTH GET_BOTH_RANGE GET_RECNO JOIN_ITEM LAST NEXT NEXT_DUP NEXT_NODUP PREV PREV_DUP PREV_NODUP SET SET_RANGE SET_RECNO READ_UNCOMMITTED MULTIPLE MULTIPLE_KEY RMW
		240	db_c_pget (DBC dbc, SV key, SV pkey, SV data, U32 flags = 0, SV *callback = &PL_sv_undef)
		241	db_c_del (DBC dbc, U32 flags = 0, SV callback = &PL_sv_undef)
		242
		243	db_sequence_open (DB_SEQUENCE seq, DB_TXN_ornull txnid, SV key, U32 flags = 0, SV callback = &PL_sv_undef)
		244	flags: CREATE EXCL
		245	db_sequence_close (DB_SEQUENCE seq, U32 flags = 0, SV callback = &PL_sv_undef)
		246	db_sequence_get (DB_SEQUENCE seq, DB_TXN_ornull txnid, int delta, SV seq_value, U32 flags = DB_TXN_NOSYNC, SV callback = &PL_sv_undef)
		247	flags: TXN_NOSYNC
		248	db_sequence_remove (DB_SEQUENCE seq, DB_TXN_ornull txnid = 0, U32 flags = 0, SV *callback = &PL_sv_undef)
		249	flags: TXN_NOSYNC
		250
		251	=head3 db_txn_finish (DB_TXN txn, U32 flags = 0, SV callback = &PL_sv_undef)
		252
		253	This is not actually a Berkeley DB function but a BDB module
		254	extension. The background for this exytension is: It is very annoying to
		255	have to check every single BDB function for error returns and provide a
		256	codepath out of your transaction. While the BDB module still makes this
		257	possible, it contains the following extensions:
		258
		259	When a transaction-protected function returns any operating system
		260	error (errno > 0), BDB will set the C<TXN_DEADLOCK> flag on the
		261	transaction. This flag is also set by Berkeley DB functions themselves
		262	when an operation fails with LOCK_DEADLOCK, and it causes all further
		263	operations on that transaction (including C<db_txn_commit>) to fail.
		264
		265	The C<db_txn_finish> request will look at this flag, and, if it is set,
		266	will automatically call C<db_txn_abort> (setting errno to C<LOCK_DEADLOCK>
		267	if it isn't set to something else yet). If it isn't set, it will call
		268	C<db_txn_commit> and return the error normally.
		269
		270	How to use this? Easy: just write your transaction normally:
		271
		272	my $txn = $db_env->txn_begin;
		273	db_get $db, $txn, "key", my $data;
		274	db_put $db, $txn, "key", $data + 1 unless $! == BDB::NOTFOUND;
		275	db_txn_finish $txn;
		276	die "transaction failed" if $!;
		277
		278	That is, handle only the expected errors. If something unexpected happens
		279	(EIO, LOCK_NOTGRANTED or a deadlock in either db_get or db_put), then the remaining
		280	requests (db_put in this case) will simply be skipped (they will fail with
		281	LOCK_DEADLOCK) and the transaction will be aborted.
		282
		283	You can use the C<< $txn->failed >> method to check wether a transaction
		284	has failed in this way and abort further processing (excluding
		285	C<db_txn_finish>).
		286
		287	=head2 DB_ENV/database environment methods
		288
		289	Methods available on DB_ENV/$env handles:
		290
		291	DESTROY (DB_ENV_ornull *env)
		292	CODE:
		293	if (env)
		294	env->close (env, 0);
		295
		296	$int = $env->set_data_dir (const char *dir)
		297	$int = $env->set_tmp_dir (const char *dir)
		298	$int = $env->set_lg_dir (const char *dir)
		299	$int = $env->set_shm_key (long shm_key)
		300	$int = $env->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		301	$int = $env->set_flags (U32 flags, int onoff = 1)
		302	$int = $env->log_set_config (U32 flags, int onoff = 1) (v4.7)
		303	$int = $env->set_intermediate_dir_mode (const char *modestring) (v4.7)
		304	$env->set_errfile (FILE *errfile = 0)
		305	$env->set_msgfile (FILE *msgfile = 0)
		306	$int = $env->set_verbose (U32 which, int onoff = 1)
		307	$int = $env->set_encrypt (const char *password, U32 flags = 0)
		308	$int = $env->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		309	$int = $env->set_mp_max_openfd (int maxopenfd);
		310	$int = $env->set_mp_max_write (int maxwrite, int maxwrite_sleep);
		311	$int = $env->set_mp_mmapsize (int mmapsize_mb)
		312	$int = $env->set_lk_detect (U32 detect = DB_LOCK_DEFAULT)
		313	$int = $env->set_lk_max_lockers (U32 max)
		314	$int = $env->set_lk_max_locks (U32 max)
		315	$int = $env->set_lk_max_objects (U32 max)
		316	$int = $env->set_lg_bsize (U32 max)
		317	$int = $env->set_lg_max (U32 max)
		318	$int = $env->mutex_set_increment (U32 increment)
		319	$int = $env->mutex_set_tas_spins (U32 tas_spins)
		320	$int = $env->mutex_set_max (U32 max)
		321	$int = $env->mutex_set_align (U32 align)
		322
		323	$txn = $env->txn_begin (DB_TXN_ornull *parent = 0, U32 flags = 0)
		324	flags: READ_COMMITTED READ_UNCOMMITTED TXN_NOSYNC TXN_NOWAIT TXN_SNAPSHOT TXN_SYNC TXN_WAIT TXN_WRITE_NOSYNC
		325	$txn = $env->cdsgroup_begin; (v4.5)
		326
		327	=head3 Example:
		328
		329	use AnyEvent;
		330	use BDB;
		331
		332	our $FH; open $FH, "<&=" . BDB::poll_fileno;
		333	our $WATCHER = AnyEvent->io (fh => $FH, poll => 'r', cb => \&BDB::poll_cb);
		334
		335	BDB::min_parallel 8;
		336
		337	my $env = db_env_create;
		338
		339	mkdir "bdtest", 0700;
		340	db_env_open
		341	$env,
		342	"bdtest",
		343	BDB::INIT_LOCK \| BDB::INIT_LOG \| BDB::INIT_MPOOL \| BDB::INIT_TXN \| BDB::RECOVER \| BDB::USE_ENVIRON \| BDB::CREATE,
		344	0600;
		345
		346	$env->set_flags (BDB::AUTO_COMMIT \| BDB::TXN_NOSYNC, 1);
		347
		348
		349	=head2 DB/database methods
		350
		351	Methods available on DB/$db handles:
		352
		353	DESTROY (DB_ornull *db)
		354	CODE:
		355	if (db)
		356	{
		357	SV env = (SV )db->app_private;
		358	db->close (db, 0);
		359	SvREFCNT_dec (env);
		360	}
		361
		362	$int = $db->set_cachesize (U32 gbytes, U32 bytes, int ncache = 0)
		363	$int = $db->set_flags (U32 flags)
		364	flags: CHKSUM ENCRYPT TXN_NOT_DURABLE
		365	Btree: DUP DUPSORT RECNUM REVSPLITOFF
		366	Hash: DUP DUPSORT
		367	Queue: INORDER
		368	Recno: RENUMBER SNAPSHOT
		369
		370	$int = $db->set_encrypt (const char *password, U32 flags)
		371	$int = $db->set_lorder (int lorder)
		372	$int = $db->set_bt_minkey (U32 minkey)
		373	$int = $db->set_re_delim (int delim)
		374	$int = $db->set_re_pad (int re_pad)
		375	$int = $db->set_re_source (char *source)
		376	$int = $db->set_re_len (U32 re_len)
		377	$int = $db->set_h_ffactor (U32 h_ffactor)
		378	$int = $db->set_h_nelem (U32 h_nelem)
		379	$int = $db->set_q_extentsize (U32 extentsize)
		380
		381	$dbc = $db->cursor (DB_TXN_ornull *txn = 0, U32 flags = 0)
		382	flags: READ_COMMITTED READ_UNCOMMITTED WRITECURSOR TXN_SNAPSHOT
		383	$seq = $db->sequence (U32 flags = 0)
		384
		385	=head3 Example:
		386
		387	my $db = db_create $env;
		388	db_open $db, undef, "table", undef, BDB::BTREE, BDB::AUTO_COMMIT \| BDB::CREATE \| BDB::READ_UNCOMMITTED, 0600;
		389
		390	for (1..1000) {
		391	db_put $db, undef, "key $_", "data $_";
		392
		393	db_key_range $db, undef, "key $_", my $keyrange;
		394	my ($lt, $eq, $gt) = @$keyrange;
		395	}
		396
		397	db_del $db, undef, "key $_" for 1..1000;
		398
		399	db_sync $db;
		400
		401
		402	=head2 DB_TXN/transaction methods
		403
		404	Methods available on DB_TXN/$txn handles:
		405
		406	DESTROY (DB_TXN_ornull *txn)
		407	CODE:
		408	if (txn)
		409	txn->abort (txn);
		410
		411	$int = $txn->set_timeout (NV timeout_seconds, U32 flags = SET_TXN_TIMEOUT)
		412	flags: SET_LOCK_TIMEOUT SET_TXN_TIMEOUT
		413
		414	$bool = $txn->failed
		415	# see db_txn_finish documentation, above
		416
		417
		418	=head2 DBC/cursor methods
		419
		420	Methods available on DBC/$dbc handles:
		421
		422	DESTROY (DBC_ornull *dbc)
		423	CODE:
		424	if (dbc)
		425	dbc->c_close (dbc);
		426
		427	$int = $cursor->set_priority ($priority = PRIORITY_*) (v4.6)
		428
		429	=head3 Example:
		430
		431	my $c = $db->cursor;
		432
		433	for (;;) {
		434	db_c_get $c, my $key, my $data, BDB::NEXT;
		435	warn "<$!,$key,$data>";
		436	last if $!;
		437	}
		438
		439	db_c_close $c;
		440
		441
		442	=head2 DB_SEQUENCE/sequence methods
		443
		444	Methods available on DB_SEQUENCE/$seq handles:
		445
		446	DESTROY (DB_SEQUENCE_ornull *seq)
		447	CODE:
		448	if (seq)
		449	seq->close (seq, 0);
		450
		451	$int = $seq->initial_value (db_seq_t value)
		452	$int = $seq->set_cachesize (U32 size)
		453	$int = $seq->set_flags (U32 flags)
		454	flags: SEQ_DEC SEQ_INC SEQ_WRAP
		455	$int = $seq->set_range (db_seq_t min, db_seq_t max)
		456
		457	=head3 Example:
		458
		459	my $seq = $db->sequence;
		460
		461	db_sequence_open $seq, undef, "seq", BDB::CREATE;
		462	db_sequence_get $seq, undef, 1, my $value;
		463
		464
95	=head2 SUPPORT FUNCTIONS	465	=head1 SUPPORT FUNCTIONS
96		466
97	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION	467	=head2 EVENT PROCESSING AND EVENT LOOP INTEGRATION
98		468
99	=over 4	469	=over 4
		470
		471	=item $msg = BDB::strerror [$errno]
		472
		473	Returns the string corresponding to the given errno value. If no argument
		474	is given, use C<$!>.
		475
		476	Note that the BDB module also patches the C<$!> variable directly, so you
		477	should be able to get a bdb error string by simply stringifying C<$!>.
100		478
101	=item $fileno = BDB::poll_fileno	479	=item $fileno = BDB::poll_fileno
102		480
103	Return the I<request result pipe file descriptor>. This filehandle must be	481	Return the I<request result pipe file descriptor>. This filehandle must be
104	polled for reading by some mechanism outside this module (e.g. Event or	482	polled for reading by some mechanism outside this module (e.g. Event or
…		…
143	interactiveness when perl is not fast enough to process all requests in	521	interactiveness when perl is not fast enough to process all requests in
144	time.	522	time.
145		523
146	For interactive programs, values such as C<0.01> to C<0.1> should be fine.	524	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
147		525
148	Example: Install an Event watcher that automatically calls	526	Example: Install an EV watcher that automatically calls
149	BDB::poll_cb with low priority, to ensure that other parts of the	527	BDB::poll_cb with low priority, to ensure that other parts of the
150	program get the CPU sometimes even under high AIO load.	528	program get the CPU sometimes even under high load.
151		529
152	# try not to spend much more than 0.1s in poll_cb	530	# try not to spend much more than 0.1s in poll_cb
153	BDB::max_poll_time 0.1;	531	BDB::max_poll_time 0.1;
154		532
155	# use a low priority so other tasks have priority	533	my $bdb_poll = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb);
156	Event->io (fd => BDB::poll_fileno,
157	poll => 'r', nice => 1,
158	cb => &BDB::poll_cb);
159		534
160	=item BDB::poll_wait	535	=item BDB::poll_wait
161		536
162	If there are any outstanding requests and none of them in the result	537	If there are any outstanding requests and none of them in the result
163	phase, wait till the result filehandle becomes ready for reading (simply	538	phase, wait till the result filehandle becomes ready for reading (simply
…		…
175		550
176	BDB::poll_wait, BDB::poll_cb	551	BDB::poll_wait, BDB::poll_cb
177		552
178	=item BDB::flush	553	=item BDB::flush
179		554
180	Wait till all outstanding AIO requests have been handled.	555	Wait till all outstanding BDB requests have been handled.
181		556
182	Strictly equivalent to:	557	Strictly equivalent to:
183		558
184	BDB::poll_wait, BDB::poll_cb	559	BDB::poll_wait, BDB::poll_cb
185	while BDB::nreqs;	560	while BDB::nreqs;
186		561
187	=back	562	=back
188		563
189	=head3 CONTROLLING THE NUMBER OF THREADS	564	=head2 VERSION CHECKING
		565
		566	BerkeleyDB comes in various versions, many of them have minor
		567	incompatibilities. This means that traditional "at least version x.x"
		568	checks are often not sufficient.
		569
		570	Example: set the log_autoremove option in a way compatible with <v4.7 and
		571	v4.7. Note the use of & on the constants to avoid triggering a compiletime
		572	bug when the symbol isn't available.
		573
		574	$DB_ENV->set_flags (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
		575	$DB_ENV->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;
190		576
191	=over 4	577	=over 4
192		578
		579	=item BDB::VERSION
		580
		581	The C<BDB::VERSION> function, when called without arguments, returns the
		582	Berkeley DB version as a v-string (usually with 3 components). You should
		583	use C<lt> and C<ge> operators exclusively to make comparisons.
		584
		585	Example: check for at least version 4.7.
		586
		587	BDB::VERSION ge v4.7 or die;
		588
		589	=item BDB::VERSION min-version
		590
		591	Returns true if the BDB version is at least the given version (specified
		592	as a v-string), false otherwise.
		593
		594	Example: check for at least version 4.5.
		595
		596	BDB::VERSION v4.7 or die;
		597
		598	=item BDB::VERSION min-version, max-version
		599
		600	Returns true of the BDB version is at least version C<min-version> (specify C<undef> or C<v0> for any minimum version)
		601	and less then C<max-version>.
		602
		603	Example: check wether version is strictly less then v4.7.
		604
		605	BDB::VERSION v0, v4.7
		606	or die "version 4.7 is not yet supported";
		607
		608	=back
		609
		610	=cut
		611
		612	sub VERSION {
		613	# I was dumb enough to override the VERSION method here, so let's try
		614	# to fix it up.
		615
		616	if ($_[0] eq __PACKAGE__) {
		617	$VERSION
		618	} else {
		619	if (@_ > 0) {
		620	return undef if VERSION_v lt $_[0];
		621	if (@_ > 1) {
		622	return undef if VERSION_v ge $_[1];
		623	}
		624	}
		625
		626	VERSION_v
		627	}
		628	}
		629
		630	=head2 CONTROLLING THE NUMBER OF THREADS
		631
		632	=over 4
		633
193	=item BDB::min_parallel $nthreads	634	=item BDB::min_parallel $nthreads
194		635
195	Set the minimum number of AIO threads to C<$nthreads>. The current	636	Set the minimum number of BDB threads to C<$nthreads>. The current
196	default is C<8>, which means eight asynchronous operations can execute	637	default is C<8>, which means eight asynchronous operations can execute
197	concurrently at any one time (the number of outstanding requests,	638	concurrently at any one time (the number of outstanding requests,
198	however, is unlimited).	639	however, is unlimited).
199		640
200	BDB starts threads only on demand, when an AIO request is queued and	641	BDB starts threads only on demand, when an BDB request is queued and
201	no free thread exists. Please note that queueing up a hundred requests can	642	no free thread exists. Please note that queueing up a hundred requests can
202	create demand for a hundred threads, even if it turns out that everything	643	create demand for a hundred threads, even if it turns out that everything
203	is in the cache and could have been processed faster by a single thread.	644	is in the cache and could have been processed faster by a single thread.
204		645
205	It is recommended to keep the number of threads relatively low, as some	646	It is recommended to keep the number of threads relatively low, as some
…		…
210	Under most circumstances you don't need to call this function, as the	651	Under most circumstances you don't need to call this function, as the
211	module selects a default that is suitable for low to moderate load.	652	module selects a default that is suitable for low to moderate load.
212		653
213	=item BDB::max_parallel $nthreads	654	=item BDB::max_parallel $nthreads
214		655
215	Sets the maximum number of AIO threads to C<$nthreads>. If more than the	656	Sets the maximum number of BDB threads to C<$nthreads>. If more than the
216	specified number of threads are currently running, this function kills	657	specified number of threads are currently running, this function kills
217	them. This function blocks until the limit is reached.	658	them. This function blocks until the limit is reached.
218		659
219	While C<$nthreads> are zero, aio requests get queued but not executed	660	While C<$nthreads> are zero, aio requests get queued but not executed
220	until the number of threads has been increased again.	661	until the number of threads has been increased again.
…		…
255		696
256	You can still queue as many requests as you want. Therefore,	697	You can still queue as many requests as you want. Therefore,
257	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	698	C<max_oustsanding> is mainly useful in simple scripts (with low values) or
258	as a stop gap to shield against fatal memory overflow (with large values).	699	as a stop gap to shield against fatal memory overflow (with large values).
259		700
260	=item BDB::set_sync_prepare $cb	701	=item $old_cb = BDB::set_sync_prepare $cb
261		702
262	Sets a callback that is called whenever a request is created without an	703	Sets a callback that is called whenever a request is created without an
263	explicit callback. It has to return two code references. The first is used	704	explicit callback. It has to return two code references. The first is used
264	as the request callback, and the second is called to wait until the first	705	as the request callback (it should save the return status), and the second
265	callback has been called. The default implementation works like this:	706	is called to wait until the first callback has been called (it must set
		707	C<$!> to the return status).
		708
		709	This mechanism can be used to include BDB into other event mechanisms,
		710	such as L<Coro::BDB>.
		711
		712	To allow other, callback-based, events to be executed while callback-less
		713	ones are run, you could use this sync prepare function:
266		714
267	sub {	715	sub {
268	my $status;	716	my $status;
269	(	717	(
270	sub { $status = $! },	718	sub { $status = $! },
271	sub { BDB::poll while !defined $status; $! = $status },	719	sub { BDB::poll while !defined $status; $! = $status },
272	)	720	)
273	}	721	}
274		722
		723	It works by polling for results till the request has finished and then
		724	sets C<$!> to the return value. This means that if you don't use a
		725	callback, BDB would simply fall back to synchronous operations.
		726
		727	By default, or if the sync prepare function is set to C<undef>, is to
		728	execute callback-less BDB requests in the foreground thread, setting C<$!>
		729	to the return value, without polling for other events.
		730
275	=back	731	=back
276		732
277	=head3 STATISTICAL INFORMATION	733	=head2 STATISTICAL INFORMATION
278		734
279	=over 4	735	=over 4
280		736
281	=item BDB::nreqs	737	=item BDB::nreqs
282		738
…		…
300		756
301	=back	757	=back
302		758
303	=cut	759	=cut
304		760
305	set_sync_prepare {	761	set_sync_prepare (undef);
306	my $status;
307	(
308	sub {
309	$status = $!;
310	},
311	sub {
312	BDB::poll while !defined $status;
313	$! = $status;
314	},
315	)
316	};
317		762
318	min_parallel 8;	763	min_parallel 8;
319		764
320	END { flush }	765	END { flush }
321		766
322	1;	767	1;
323		768
		769	=head1 COMMON PITFALLS
		770
		771	=head2 Unexpected Crashes
		772
		773	Remember that, by default, BDB will execute requests in parallel, in
		774	somewhat random order. That means that it is easy to run a C<db_get>
		775	request on thesa me database as a concurrent C<db_close> request, leading
		776	to a crash, silent data corruption, eventually the next world war on
		777	terrorism.
		778
		779	If you only ever use foreground requests (without a callback), this will
		780	not be an issue.
		781
		782	=head2 Unexpected Freezes or Deadlocks
		783
		784	Remember that, by default, BDB will execute requests in parallel, which
		785	easily leads to deadlocks (even concurrent put's on the same database can
		786	deadlock).
		787
		788	You either need to run deadlock detection (and handle the resulting
		789	errors), or make sure only one process ever updates the database, ine one
		790	thread, e.g. by using only foreground requests (without a callback).
		791
324	=head2 FORK BEHAVIOUR	792	=head1 FORK BEHAVIOUR
325		793
326	This module should do "the right thing" when the process using it forks:	794	This module should do "the right thing" when the process using it forks:
327		795
328	Before the fork, IO::AIO enters a quiescent state where no requests	796	Before the fork, BDB enters a quiescent state where no requests
329	can be added in other threads and no results will be processed. After	797	can be added in other threads and no results will be processed. After
330	the fork the parent simply leaves the quiescent state and continues	798	the fork the parent simply leaves the quiescent state and continues
331	request/result processing, while the child frees the request/result queue	799	request/result processing, while the child frees the request/result queue
332	(so that the requests started before the fork will only be handled in the	800	(so that the requests started before the fork will only be handled in the
333	parent). Threads will be started on demand until the limit set in the	801	parent). Threads will be started on demand until the limit set in the
334	parent process has been reached again.	802	parent process has been reached again.
335		803
336	In short: the parent will, after a short pause, continue as if fork had	804	In short: the parent will, after a short pause, continue as if fork had
337	not been called, while the child will act as if IO::AIO has not been used	805	not been called, while the child will act as if BDB has not been used
338	yet.	806	yet.
339		807
		808	Win32 note: there is no fork on win32, and perls emulation of it is too
		809	broken to be supported, so do not use BDB in a windows pseudo-fork, better
		810	yet, switch to a more capable platform.
		811
340	=head2 MEMORY USAGE	812	=head1 MEMORY USAGE
341		813
342	Per-request usage:	814	Per-request usage:
343		815
344	Each aio request uses - depending on your architecture - around 100-200	816	Each aio request uses - depending on your architecture - around 100-200
345	bytes of memory. In addition, stat requests need a stat buffer (possibly	817	bytes of memory. In addition, stat requests need a stat buffer (possibly
346	a few hundred bytes), readdir requires a result buffer and so on. Perl	818	a few hundred bytes), readdir requires a result buffer and so on. Perl
347	scalars and other data passed into aio requests will also be locked and	819	scalars and other data passed into aio requests will also be locked and
348	will consume memory till the request has entered the done state.	820	will consume memory till the request has entered the done state.
349		821
350	This is now awfully much, so queuing lots of requests is not usually a	822	This is not awfully much, so queuing lots of requests is not usually a
351	problem.	823	problem.
352		824
353	Per-thread usage:	825	Per-thread usage:
354		826
355	In the execution phase, some aio requests require more memory for	827	In the execution phase, some aio requests require more memory for
356	temporary buffers, and each thread requires a stack and other data	828	temporary buffers, and each thread requires a stack and other data
357	structures (usually around 16k-128k, depending on the OS).	829	structures (usually around 16k-128k, depending on the OS).
358		830
		831	=head1 WIN32 FILENAMES/DATABASE NAME MESS
		832
		833	Perl on Win32 supports only ASCII filenames (the reason is that it abuses
		834	an internal flag to store wether a filename is Unicode or ANSI, but that
		835	flag is used for somethign else in the perl core, so there is no way to
		836	detect wether a filename is ANSI or Unicode-encoded). The BDB module
		837	tries to work around this issue by assuming that the filename is an ANSI
		838	filename and BDB was built for unicode support.
		839
359	=head1 KNOWN BUGS	840	=head1 KNOWN BUGS
360		841
361	Known bugs will be fixed in the next release.	842	Known bugs will be fixed in the next release, except:
		843
		844	If you use a transaction in any request, and the request returns
		845	with an operating system error or DB_LOCK_NOTGRANTED, the internal
		846	TXN_DEADLOCK flag will be set on the transaction. See C<db_txn_finish>,
		847	above.
362		848
363	=head1 SEE ALSO	849	=head1 SEE ALSO
364		850
365	L<Coro::AIO>.	851	L<AnyEvent::BDB> (event loop integration), L<Coro::BDB> (more natural
		852	syntax), L<IO::AIO> (nice to have).
366		853
367	=head1 AUTHOR	854	=head1 AUTHOR
368		855
369	Marc Lehmann <schmorp@schmorp.de>	856	Marc Lehmann <schmorp@schmorp.de>
370	http://home.schmorp.de/	857	http://home.schmorp.de/

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Comparing BDB/BDB.pm (file contents): Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs. Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC

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Comparing BDB/BDB.pm (file contents):
Revision 1.8 by root, Wed May 9 06:42:23 2007 UTC vs.
Revision 1.53 by root, Tue Oct 21 02:21:25 2008 UTC